Squid (weapon)

• 1. Introduction

  ›

  Squid was a British World War II anti-submarine weapon that turned the mathematics of underwater warfare on its head. Where the standard British depth charge needed more than 60 attacks to sink a single submarine, Squid needed fewer than three. That ratio tells a quiet, startling story about one of the most effective naval weapons the war produced. How did a mortar ordered straight from the drawing board in 1942 end up reshaping the way ships hunted submarines? And why, despite its record, did some officers fight to keep it off their ships?

• 2. Rush to Service

  ›

  In 1942, Britain's Directorate of Miscellaneous Weapons Development ordered Squid directly from the drawing board, bypassing the usual development cycle. The weapon was rushed into service in May 1943 aboard HMS Ambuscade. The first production unit then went to HMS Hadleigh Castle, and from there installations spread to 70 frigates and corvettes before the war ended.

  The design itself was a three-barrel 12-inch mortar. The barrels were mounted in series but angled away from each other so the projectiles would scatter rather than cluster. A rotating frame allowed the entire assembly to swing 90 degrees, bringing the barrels into position for loading. Each projectile weighed 390 pounds, with a 207-pound minol II charge at its core.

  The fuzing system was one of the weapon's quiet innovations. A clockwork time fuze set the detonation depth, and that depth could be updated continuously right up to the moment of firing. This meant a ship could track a diving submarine and adjust the attack in real time. The maximum depth the weapon could reach was 900 feet.

• 3. The Triangle Pattern

  ›

  HMS Loch Killin made history on the 31st of July 1944, becoming the first ship to achieve a successful Squid attack when she sank a submarine. The outcome was shaped by how the weapon was designed to detonate. Squid's three projectiles formed a triangle roughly 40 yards on a side, landing about 275 yards ahead of the firing ship. Most installations used two sets of mortars, so all six bombs went out in a single salvo, creating two opposing triangular spreads.

  Those spreads were set to explode 25 feet above and below the estimated position of the target. The intention was not a direct hit but a pressure wave. When both charges detonated at the correct depth, the wave crushed the submarine's hull between them. Post-war trials confirmed that this approach made Squid nine times more effective than conventional depth charges.

  The weapons were fired automatically from the sonar range recorder at the calculated moment. Because the attack happened ahead of the ship rather than alongside it, sonar contact with the target could be maintained right through to detonation, a problem that had plagued earlier systems.

• 4. The Numbers Against Convention

  ›

  Over the course of the war, Squid was credited with sinking 17 submarines in 50 attacks, a success ratio of one kill for every 2.9 attacks. The Hedgehog system, which Squid replaced, achieved 47 kills from 268 attacks, a ratio of 5.7 to 1. Conventional British depth charge attacks produced 85.5 kills from 5,174 attempts, a ratio of 60.5 to 1.

  Those comparisons sit in the source record as a precise indictment of what came before. Each improvement in the ratio represents attacks that did not need to happen, submarines that were caught rather than escaped, and ships that returned to port. By 1959, the total number of Squid installations produced had reached 195.

  Despite the figures, adoption was not universal. Royal Canadian Navy Captain Kenneth Adams was among the officers who openly opposed fitting Squid to escorts. His argument was practical rather than sceptical of the weapon itself: installing the mortar meant removing guns, and a ship without adequate guns was unsuitable for fleet actions. The tension between anti-submarine effectiveness and general combat capability was a real constraint on how widely Squid could be deployed.

• 5. After the War

  ›

  The Royal Navy's last operational firing of Squid took place in April 1977, when the Type 61 frigate Salisbury discharged the weapon in service for the final time. The system had already been superseded by the Limbo system, which followed Squid in the lineage of British ship-mounted anti-submarine mortars.

  The Swedish Navy kept Squid in use longer than Britain did. The Östergötland-class destroyers carried the system until 1982, when they were decommissioned. Physical examples of the mortars survived into the preservation era. The Explosion! Museum of Naval Firepower in Gosport, Hampshire holds a display example, and another can be found at Devonport Naval Base. A preserved ship fitted with the system is part of the historic ships collection at the Historic Dockyard in Chatham, Kent. Further examples are on display in Hamilton, Ontario and at the naval museum in Malacca, Malaysia, marking how widely the weapon spread across allied and Commonwealth navies.